A handle returning apparatus for returning an operation handle that is rotationally operated to a neutral position by an elastic force of a spring member is known. For example, JP2006-83983A which will be hereinafter referred to as Reference 1 discloses a seat lifting apparatus including a lever-type operation handle that is rotationally operated in a first direction and a second direction (i.e., an up-down direction) including a neutral position. The seat lifting apparatus disclosed in Reference 1 also includes an input member that rotates in conjunction with the operation handle and a spring member that includes a spring portion in an arc form (substantially in a C-shape) extending around a rotation axis of the input member. The spring member includes opposed end portions which are away from each other in a circumferential direction, one of the end portions engaging with the input member and the other of the end portions engaging with a fixation member. Accordingly, the input member is biased so that a returning force for returning the operation handle to the neutral position is generated in the handle returning apparatus.
Specifically, the input member rotates relative to the fixation member based on the rotation operation of the operation handle so that the spring member is resiliently or elastically deformed in a manner that the opposed end portions of the spring members are resiliently forced apart from each other. Based on a returning force, i.e., an elastic force, generated by the spring member that is resiliently deformed, the operation handle which is pivotally operated may return to the neutral position.
Nevertheless, in the seat lifting apparatus disclosed in Reference 1, in a case where a difference in operation amount (rotation operation amount) of the operation handle occurs depending on a direction of rotation operation of the operation handle, a difference in possible returning force, specifically, in maximum value of possible returning force, may be generated. For example, in a configuration where the operation handle is provided at a side of a vehicle seat in a width direction thereof as in the seat lifting apparatus in Reference 1, it may be difficult to increase the rotation operation amount of the operation handle in a case where the operation handle is pulled downward as compared to a case where the operation handle is lifted upward. Thus, the resulting difference in returning speed and operation reaction force of the operation handle between the cases where the operation handle is pulled downward and where the operation handle is lifted upward affects returning performance of the operation handle, which may be a cause of decrease of operation feeling of the operation handle.
A need thus exists for a handle returning apparatus and a seat lifting apparatus for a vehicle which are not susceptible to the drawback mentioned above.